The inventive concepts described herein pertain to tables and, more particularly, to a vertical and adjustable support for tables or the like.
Tables are used in many different environments for many different purposes. For instance, in an office environment, tables may be used in a partition space as a desk top to support a seated person, as a monitor support, as a conferencing table for seated conferees, as a standing conferencing table, as a work station supporting surface for a standing person, etc. Where tables are used for many different applications, ideally, the tables are constructed to have task specific heights that are ergonomically correct. For instance, in the case of a desk top for use by a seated user, a surface top height should be approximately 28 to 30 inches above a supporting floor. As another instance, in the case of a desk top for use by a standing user, the surface height should be approximately 42 to 45 inches above a supporting floor. Many other surface heights are optimal for other tasks.
In order to reduce the number of tables required to support different tasks within an environment, adjustable height tables have been developed that allow a user to modify table height to provide table surfaces at task optimized heights. Thus, for instance, some exemplary adjustable tables include leg structure including a lower column mounted to a base support and an upper column that is received within an internal channel formed by the lower column and telescopes therefrom and a table top that is mounted to the top end of the lower column. Here, a locking mechanism is provided to lock the relative juxtapositions of the upper and lower columns. To adjust table top height, the locking mechanism is unlocked and the upper column is extended from the lower column until a desired height is reached after which the locking mechanism is again locked.
One particularly advantageously table configuration includes a single pedestal type support structure disposed below a table top. In addition to being aesthetically pleasing, a single pedestal structure facilitates additional design options, especially where the single pedestal structure can be off table top center (e.g., closer to a rear table top edge than to an oppositely facing front table top edge).
One problem with telescoped upper and lower columns that support a table top is that the upper column, table top and load thereon are often relatively heavy and therefore difficult for a person to raise and lower in a controlled fashion. One solution to the weight problem has been to provide a counterbalance assembly in conjunction with a height adjustable table that, as the label implies, compensates for or balances at least a portion of the combined weight of the upper column, table top and load thereon.
One exemplary single pedestal counterbalancing system is described in U.S. Pat. No. 3,675,597 (hereinafter “the '597 patent”) which includes a metal roll type spring mounted near the top end of an upper column, a pulley mounted near the bottom of the upper column and a cable having a central portion supported by the pulley and first and second ends that extend up to the top end of a lower stationary column and to a free end of the spring. The spring is in a normally wound state when the upper column is in a raised position and is in an extended a loaded state when the upper column is lowered into the lower column. Thus, the spring provides a counterbalance force that tends to drive the upper column and table top mounted thereto upward.
While the solution described in the '597 patent can be employed in a single pedestal type support structure, this solution has several shortcomings. First, this solution provides no way of conveniently adjusting the counterbalance force to compensate for different table top loads. To this end, because table top loads often vary appreciably, it is advantageous to provide some type of mechanism that allows the counterbalance force to be adjusted within some anticipated range (e.g., 50 to 300 pounds). In the case of the '597 patent, counterbalance adjustment is accomplished by adding additional springs (see FIGS. 11 and 12) which is a cumbersome task at best and, in most cases, likely would be completely avoided by a table user.
Second, the '597 patent solution fails to provide a safety mechanism for arresting upper column movement when the table top is either overloaded or, given a specific counterbalance force, under loaded. Thus, for instance, if the tabletop load is much greater than the counterbalance force when a locking mechanism is unlocked, the table top and load will drop quickly and unexpectedly. Similarly, if the table top load is much smaller than the counterbalance force is on the table top when the locking mechanism is unlocked, the table top and load would rise quickly and unexpectedly. Unexpected table movement can be hazardous.
Third, the amount of counterbalance force required to aid in raising the upper column, table top and load thereon in the '597 patent, in addition to depending on the size of the load, also depends on the distribution of the load. In this regard, a considerable amount of friction results when the upper column moves with respect to the lower column as at least portions of the upper and lower columns make direct contact during movement. The amount of friction is exacerbated if the load on the table top is unevenly distributed. Thus, for instance, if the load is located proximate one edge of the table top instead of directly over the pedestal support, the upper column will be somewhat cantilevered from the lower column and greater friction will occur—thus the same load can have appreciably different effects on the required counterbalancing force required to be effective.
U.S. Pat. No. 6,443,075 (hereinafter “the '075 patent”) describes a table system that includes many of the features that the '597 patent solution lacks, albeit in the context of a configuration that includes two upper columns as opposed to a single column. To this end, the '075 patent teaches two raisable columns supported by a base where a release mechanism is operable to attempt to release a locking mechanism which, when unlocked, allows a table top to be moved upward or downward along a table stroke. Here, a spring loaded cam member operates as a counterbalance mechanism.
The '075 patent also teaches a mechanism for adjusting the counterbalancing assembly so that different counterbalance forces can be dialed in to compensate for different table top loads. Thus, for instance, where it is contemplated that a computer monitor may be placed on and removed from a table top at different times, by providing an adjustable counterbalance assembly, the changing load can be effectively compensated and the force required by a person attempting to change table top height can be minimized.
The '075 patent further teaches a safety mechanism for, when the locking mechanism is unlocked, prohibiting downward table movement when the table top load is greater than some maximum load level associated with a safe rate of table top descent. Similarly, the '075 patent teaches a safety mechanism for, when the locking mechanism is unlocked, prohibiting upward table movement when the table top is under loaded to an extent greater than some minimum load level associated with a safe rate of table top ascent.
While the solution described in the '075 patent has many advantageous features, unfortunately the solution also has several shortcomings. First, while the '075 patent teaches an overload/under load safety mechanism, the safety mechanism is only partially effective. To this end, the safety mechanism taught by the '075 patent works when a table top is over or under loaded when a locking mechanism is unlocked. However, if table load changes while the locking mechanism is unlocked and the table is either moving up or down (i.e., a person places a heavy box on the table top or removes a heavy box from the top), the overload/underload protection mechanism will not activate and the table top will either rise or drop quickly and unexpectedly.
Second, the '075 patent solution is designed for raising two columns, not one, and requires space between the two columns for accommodating various components. Thus, the '075 patent solution includes components that cannot be concealed within a single telescoping type column configuration which is preferred for many applications for aesthetic as well as design and space saving reasons.
Third, the '075 patent solution does not appear to facilitate a constant upward force on the upper column and table top irrespective of the height of the table top along its stroke as is desired in many applications. Instead, the upward force appears to be variable along the table top stroke and to depend at least in part on table top height.
Fourth, the '075 patent solution requires a table user to either modify table top load or manually adjust the counterbalance force when a load and the counterbalance force are not sufficiently balanced prior to changing the table top height. Here, changing the counterbalance force can be a tedious task as the table user has to estimate the amount of unbalance when adjusting the required amount of counterbalance which, in most cases, would be an iterative process.
Fifth, assuming the counterbalance force is similar to a table load when the locking mechanism is unlocked, the '075 patent appears to allow fast table top movement. For instance, when the locking mechanism is unlocked, a table user can force the table top up or down very quickly. While fast table top movement may seem advantageous, rapid movement can cause excessive wear and even damage to assembly components. For example, if the top is forced rapidly downward toward the end of the movement stroke, the moveable column components may collide with excessive force with the stationary components. As another example, if the locking mechanism is released while the table top is rapidly descending, the locking mechanism could be damaged as movement of the moving column is halted. Similarly, if the top moves to rapidly, items such as displays, printers, etc., supported by the top could be damaged.
Thus, it would be advantageous to have a simplified counterbalancing assembly that could be mounted within a single column type support structure. It would also be advantageous to have a safety locking mechanism for use in a single column where the safety locking mechanism operates any time an overload condition or an under load condition occurs. In at least some cases it would be advantageous if the counterbalancing mechanism were adjustable. Moreover, in at least some cases it would be advantageous if the maximum up and down speed of the table top were controlled.